Ⅰ异特窗酸类化合物的高效合成方法研究Ⅱ P-Phos在胺偶联反应中的应用及其二氧化硅负载催化剂在前手性酮不对称还原中的应用

【作者】 陈欢生；

【导师】 陶凤岗； 王全瑞；

【作者基本信息】 复旦大学 ， 有机化学， 2008， 博士

【摘要】 化学科学与化学工程技术的进步为国民经济增长、人民群众生活水平的提高与社会的发展作出了十分重要的贡献。但另外一方面,传统的化学工业也产生了大量的工业污染,造成了严重的环境问题,危及到可持续发展。由此专家学者们提出了与传统治理污染不同的“绿色化学”概念,它是从源头解决污染问题的一门科学。理想的绿色化学对有机合成反应的要求是:1)高选择性,极少副产品,最好100%选择性;2)原子经济性,实现零排放;3)采用无毒、无害的原料;4)采用无毒、无害的催化剂和溶剂;5)高转化率。本论文以绿色化学为主线,介绍了两方面的工作:1.异特窗酸类化合物的高效合成方法研究;2.P-Phos在胺偶联反应中的应用及其二氧化硅负载手性催化剂在前手性酮不对称还原中的应用。本论文的第一部分工作:第二章我们以α-酮酸酯为基本原料,筛选了碱碱偶(B1/B2)作用体系,利用其催化活性的差异,实现了一瓶多组分多步系列反应,将Aldol缩合或Homo-aldol缩合、内酯化关环、3-OH衍生化等多个步骤连续协调地进行,发展出异特窗酸衍生物的高效合成方法。通过变换不同的烷基化/酰基化试剂或者酮酸酯,我们合成了45个新的异特窗酸衍生物。当采用三甲基氯硅烷作为烷基化试剂时,由于Si-O键在酸的作用下极易水解,这也为我们高产率制备3-羟基异特窗酸提供了便捷的方法。同时,我们还对两种不同的酮酸酯之间的Aldol缩合进行了研究。本工作属于Aldol-酯交换-亲核取代三步串联反应,具有有机小分子催化的特征,符合当今绿色化学发展的趋势。所用的试剂及原料均为常见和容易制备,所得到的产物具有重要的应用潜力。与一些传统的方法比较,该策略的反应条件极其温和、操作简便、合成效率高、底物适用范围广,对于构建结构复杂的丁烯羟酸内酯类化合物具有独到的优点。因此,该方法具有良好的学术意义和合成应用价值。第三章我们对羟基异特窗酸化合物进行了进一步的衍生化。通过Suzuki反应,我们在异特窗酸的β位引入了芳基基团,合成了一系列的O-烷基化-β-芳基取代的异特窗酸化合物。在异特窗酸的β位引入了Br原子,因此该化合物同样可以用于Heck、Sonogashira等一些著名的有机反应中。这样,我们就为异特窗酸类化合物的进一步应用提供了新的途径。本论文的第二部分工作:第四章我们合成了配体P-Phos,对原有的合成方法作了些改进。将配体P-Phos应用于胺偶联反应的研究。通过对碱、溶剂和催化剂用量的筛选,确立了对胺偶联反应最优化的反应条件,该反应对溴代芳烃反应效果很好,对部分氯代芳烃,特别是氯代吡啶同样得到了令人满意的结果。该催化剂对水和空气不敏感,长期储存不失活性。对胺偶联反应的催化效果比较理想,因此是一种有应用前景的催化剂。第五章经过拆分,我们得到手性P-Phos配体,将其官能团衍生化后,负载在普通硅胶和中孔分子筛SBA-15上,得到固载手性配体。将固载手性配体分别和两种金属Ru络合,得到不同种的固载催化剂。将固载的催化剂用于前手性酮的不对称还原反应,发现配体的稳定性和催化活性很好,催化剂能够重复使用10次以上。但是,催化剂的对映选择性较差,没有获得高光学纯度的产物。更多还原

【Abstract】 So far, chemistry and chemical engineering have been regarded as the major contributors to economic progress over the past century, and yet the chemical industry is often taken to task for many serious environmental problems. One of the most attractive concepts for pollution protection is green chemistry. It is better to prevent waste than to treat or clean up waste after it is formed. Green chemistry is the design, development, and implementation of chemical products and processes to reduce or eliminate the use and generation of substances hazardous to human health and the enviroment.Green Chemistry is the main line of the whole thesis. In this thesis, we mainly discuss two parts of work. 1. An effective DBU-Et₃N-mediated one-pot synthesis of isotetronic acids fromα-ketoesters; 2. Preparation of P-Phos and its use in palladium-catalyzed amination of aryl halides with amines; Preparation of silica-supported Ru-P-Phos catalysts and use for enantioselective hydrogenation.First partIn chapter two, we have developed a convenient one-pot synthesis of isotetronic acids usingα-ketoesters as the starting marterial. The most satisfactory preparation involved the reaction using DBU along with Et₃N as the base. To our awareness, this represents the first one-pot synthesis of this interesting class of compounds and constitutes a novel homoaldol-based ABB’ three component reaction. We have synthesized 45 isotetronic acid compounds through changing the alkylated/acrylated agents orα-ketoesters. The cross-aldol coupling is also described in the thesis. The reaction is in line with the development of green chemistry. The protocol carried several notable advantages such as the wide substrates, simple operation, exceedingly mild condition, there being no use of any expensive reagents. A further advantage is that inert atmospheric condition is not necessary. Therefor the methods we have developed may have potentiality in theory and application.In chapter three, we use the simple isotetronic acids obtained in chapter two to synthesize more complex compounds. We have synthesized a series ofβ-aryl-isotetronic acids through Suzuki reaction. Theβ-bromine isotetronic acid has been synthesized, so the Heck and Sonogashira reaction can also be used in the coupling reaction.Second partIn chapter four, the racemic ligand rac-P-Phos was synthesized using a slightly modified six-step literature method starting from 2,6-dichloropyridine. An optical reaction condition was ensured after screening several bases and solvents. We then use the air-stable dipyridylphosphine ligand rac-P-Phos in the palladium catalyzed aromatic amination of haloarenes with variable amines. The yields are generally high, demonstrating that the catalytic activity of the present system matches or exceeds that of the reported phosphine ligands reported by others. The method has common benefits in other air-stable palladium catalyzed animations, such as convenient, very efficient, wide substrate scope, low catalyst dosage. Combined with the inherent stability and easy accessibility, the present method may also facilitate the large-scale usefulness of the C-N bond forming reactions.In chapter five, we have developed and optimized a practical, efficient, and highly recyclable heterogeneous catalyst through immobilization of Ru-P-Phos onto a very cheap amorphous silica gel and mesoporous silica of SBA-15 by an easily accessible approach for the first time. The catalyst immobilized on silica gel demonstrated remarkably high catalytic activities for the heterogeneous asymmetric hydrogenation of various ketones. Particularly, the catalyst could be readily recovered and reused in multiple consecutive catalytic runs （up to 10 uses）. However, the catalyst system didn’t give satisfactory e.e.% values so far.更多还原